1. Field of the Invention
The present invention relates to the field of humidifiers, and more specifically, to a humidifier and heater combination.
2. Prior Art
Humidifiers are typically used with respiratory equipment to both warm and humidify a breathable gas provided to a patient. Such gas usually consists of oxygen, air and anasthetic gas or mixtures thereof. It is also well known that where inhalation therapy is used, many components of the equipment are reusable and thus must be sterilized prior to being reused. Such prior art units are often accompanied by a number of objectionable features including the difficulty in sterilization, the inability to quickly heat the humidified gas stream and the inability to control the temperature of the gas stream delivered to the patient.
Generally, humidifiers fall into two categories, a bubble humidifier and an evaporative or pass-over type humidifier. A bubble humidifier functions by blowing air through a tube and allowing it to exit near the bottom of a water reservior and then bubble up through the water. Since the normal rise of bubbles through a short water distance does not usually provide sufficient humidification and/or heating of the gas bubble, these units are usually equipped with baffles, porous packing or the like to break up the bubbles into smaller sizes and to slow their travel. In addition, smaller size bubbles provide for increases in humidification. Such bubble humidifiers often include complex heaters in order for the water and/or the gas stream to be heated to a desired temperature.
Evaporative humidifiers are of a more recent design and are rapidly gaining acceptance because of their advantages over bubble humidifiers. In their simplest form, evaporative humidifiers allow the gas to pick up humidity by passage of the gas over a wetted surface. Efficiency, as measured by humidity increase, can be increased by increasing the area of wetted contact either in terms of two-dimensional area or by increasing surface porocity or texture. It can be further enhanced by heating the water, directly or indirectly, or by heating the evaporative surface, or by heating the air. Notwithstanding the recognition of the advantages associated with heating, the prior art has not evolved a heater which is straight forward in its design, and which can be used on other similar equipment such as a nebulizer. Thus, even though the prior art is aware of the advantages associated with evaporative humidifiers, heater design has lagged behind.
Examples of humidifiers and similar equipment is illustrated in U.S. Pat. Nos. 4,110,419; 4,225,542; 4,201,204; 3,954,290; and 4,303,601; and 4,366,105.
From a review of these references, it can be seen that most humidifers do not readily lend itself to the use of an easily removable, compact, but efficient heater. The present invention addresses these and other problems identified above with respect to the prior art.